The iteration just closed now adds to the “release notes”. After each iteration, you must re-plan the project ahead (release plan or road map). All new ideas and conclusions from the demo, evaluation and reflection must be taken into account, as the product owner prioritizes the product backlog again. Based on the measured velocity of the team or teams, a new release plan is made, fitting into the original schedule. That is, only the content of the iterations is re-planned. The meetings are still held as planned.
The schedule is not changed. The 4th iteration still ends with week number 8, and the releases are delivered in the weeks 6, 12 and 18. Only, the scope and content of the the project is adjusted empirically as the developers and customers gain understanding of the solution.